This invention relates to means for supporting nuclear fuel pins in a coolant channel of a nuclear reactor. Problems in supporting nuclear fuel pins in nuclear reactors arise from many design restraints unique to these components. For reasons of nuclear reactivity and neutron economy it is a requirement to reduce the parasytic material in a reactor core to a minimum whilst for heat transfer reasons it is desirable to avoid the use of fuel pins having a large cross-sectional area. A consequence of these design considerations is that the fuel pin tends to be a very long thin object with the fuel can of minimum thickness such that the pin with its heavy metal oxide filling is hardly self-supporting in other than a vertical attitude and it is in this attitude it must be supported in a nuclear reactor core. Typically the fuel pin may have a length/diameter ratio of 500/1 and, in the case of a fast reactor fuel pin, the outside diameter may be about 0.2 inches. Furthermore for reactor physics reasons, these long, slender, pins must be spaced very close together. As an example, a fast reactor fuel assembly may require that some 2-300 fuel pins, each a few tenths of an inch diameter, be supported end on to coolant flowing up a channel about 22 square inches in total area. Eventually, of course, the fuel pins, having suffered irradiation, must be withdrawn from the fuel channel by an upward pull which must dislodge the pin without the risk of breaching the can as a fuel (and fission product) container.
It will be appreciated from the foregoing that the design of fuel pin support can be a matter of some complexity.